It depends upon two things:
1) When your Single-Six was made, since pre-1961 Single-Six barrel's had .219" bores, and were not bored .221"-.224" for the .22 Mag until the advent of the convertibles in 1962.
Firing the larger mag slug, under somewhat higher pressure/velocity, might present problems - why Ruger went with the larger compromise bore size for the convertibles.
2) There's a finite distance, particular to each revolver (minute in some), between the throat/rear end of the barrel and the rear of the cylinder frame (aka: recoil shield), into which any cylinder must fit exactly, leaving just enough clearance up front for a proper bbl/cylinder gap.
Factory-fitted extra cylinders are not only properly timed, but also fitted to the frame with the proper gap to maintain headspace.
Yes, many cylinders will "drop in", but you almost never hear about the mistakes, where one won't.
If I wanted to buy a used cylinder, I'd measure the length of mine, both at the outer edge and the central arbor, and ask a prospective seller to measure theirs, w/o divulging my measurements.
I would only buy a cylinder exactly the same length or a bit longer (to file/fit), but not shorter - as they're mighty hard to stretch.